I need help with my pulley swap! :(

ok so. im allowed to swap my pulley's and i wanna go 4.5in or a 5in on the engine and a 3in on the trans. top speed around 30-38mph. perfect for me. I know how to do it but i dont know how i can swap the front pulley yet keep the deck drive pulley because i still mow the lawn with it. Please give me some ideas